Need help with the design of a high strength non-magnetic gear and pinion 1

[bludog]

Hi,

I need to designing a high strength non-magnetic gear and pinion for a welding application. Here are the specs:

- The gear and pinion will be located in a very high weld field and need to be non-magnetic.
- Gear and pinion need to drive 420ft.lbs of torque at about 12 RPM.
- The area these gears go is very compact and I am limited to a working center distance of about 6.5 inches and a face width of only 1 inch (for both the gear and pinion)

Using a gear design program from MITcal I have determined that the space restriction is just too much and I can't find a non-magnetic material that is strong enough not fail from contact fatigue (not bending fatigue).
Can anybody make any recommendations of a (non-magnetic) stainless steel or bronze alloy that has tensile and contact fatigue strength?

Also, what diametral pitch and number or teeth do you recommend for the gear and pinion?
Is it best I have a gear/pinion ratio of 1/1 in order to give both gears the same tooth load and minimize the chance of both components from failing?

Thanks,
Justin

 

[bludog]

Here is a PDF that shows what I envision the gear to look like.

 

[gearcutter]

Unfortunately you've asked a 'how long is a piece of string' type question.
Get hold of a gear design consultant.
The AGMA's website lists quite a few.


Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[bludog]

Thanks Ron and you are correct. However, I went to the AGMA and they certainly had a long list of references. Can you give me any recommendations of a gear design consultant that would be experienced with non magnetic metals?

Thanks,
Justin

 

[gearcutter]

I'd start with whoever is closest to your area.
Some of the materials used in corrosive industrial environments would be non-magnetic so that may be a clue as to who best to look for.

Ron Volmershausen
Brunkerville Engineering
Newcastle Australia

http://www.aussieweb.com.au/email.aspx?id=1194181

 

[tbuelna]

bludog-

In order to determine the acceptable contact stress fatigue limit for your application, you'll need to provide a description of the service loads and cycles. Given the gear diameter, ratio, face width, torque, and speed.

I ran a quick check of a 1:1 spur gearset, with each gear having 21T/3.2DP and a 1.0" face width. The flank contact stress at 420 ft-lbs input torque was around 117ksi. The only non-magnetic materials truly capable of enduring this level of contact stress that come to mind are ceramics like silicon nitride. There are some heat-treatable copper/bronze alloys, such beryllium-copper or aluminum-bronze, that can be hardened to fairly high levels, but I don't think they would have the compressive strength for the fatigue life required.

Rather than using gears, with the speed/torque required in your application, you might consider using a chain/sprocket drive. The chain links and sprocket teeth would have much lower contact stress levels than spur gear teeth for a similar torque load. The chain could be made from austenitic stainless and the sprockets could be made from bronze or aluminum.

Hope that helps.
Terry

 

[MikeHalloran]

I'd take a look at using no gears at all.

I.e., extend the driven shaft and drive it with a truck driveshaft.



Mike Halloran
Pembroke Pines, FL, USA

 

[tbuelna]

bludog-

Looking at the picture of your proposed gear drive, it would seem possible that you could use a wider gear face to reduce the contract stresses. If so, you could probably use a heat treatable aluminum-bronze material with a dry-film coating.